Analysis On The Vertical Bearing Behavior Of Slung Rock-socketed Piles In Deep And Weak Soil

China's coastal areas are generally marine sedimentary plains.Zhuhai has special geology,and there are often streamlined soft soils in the strata.The average thickness of soft soil layer in an engineering geological area of Zhuhai Free Trade Zone is 23.13 m,and the average buried depth of medium weathered rock is about 60 m.The project uses perfusion rock-socketed piles with a pile length of 55-75 m.The rock-socketed piles are usually used in projects where the settlement is strict and the upper load is large.However,due to its high bearing capacity,few field tests can be loaded into the limit state.Therefore,there are still many ambiguities in determining the load transfer characteristics and bearing capacity.In practice,some pile lengths and pile diameters are often too conservative.Unreasonable design not only increases the construction difficulty,reduces the construction efficiency,but also causes economic waste.Therefore,the research on the load transfer characteristics of slender rock-socketed piles has great theoretical and practical value.Firstly,the definition of slender rock-socketed piles is given in this paper.Combined with an example of pile foundation engineering in Zhuhai Free Trade Zone,the engineering characteristics,construction technology and construction precautions of slender rock-socketed piles in soft soil area are described in detail.The load bearing mechanism of slender rocksocketed piles.Secondly,this paper considers the law of load transfer between piled soil and pile rock.Based on the principle of limit equilibrium and the empirical strength criterion of HoekBrown rock mass,the calculation method of ultimate bearing capacity of slung rock-socketed pile is deduced,and the soft soil weak area is deduced.The load transfer process of the rock-socketed section of the slender bored pile is divided into the pile top load and settlement formulas of the elastic stage of the pile surrounding rock,the residual strength stage of the pile surrounding rock and the failure stage of the pile surrounding rock.Finally,based on the measured data of engineering static load test and finite element numerical simulation results,the rationality of the calculated formula for the vertical ultimate bearing capacity of single pile is verified,and different pile diameters,pile lengths,and lengths are analyzed by MIDAS GTS NX software.The influence of the thickness of soft soil layer and different rock-socketing depth on the vertical bearing behavior of slung rocksocketed piles.Compared with rock-socketed piles in non-soft soil area,the settlement of slender rocksocketed piles in soft soil area is mainly composed of elastic compression of pile concrete and strain of foundation rock at pile bottom.The development of lateral resistance and end resistance of slender rock-socketed piles in soft soil area is not synchronous but asynchronous.Due to the influence of pile length and depth of bedrock,the behavior of end-bearing friction piles is generally shown as the force behavior of end-bearing friction piles.